As commonly known, solar panels such as flat panel photovoltaic systems, for example, are used in renewable energy production. Mechanical tracking systems are employed with the solar panels to cause the solar panels to “track,” or concentrate towards, rotate or translate with the motion of the sun relative to the earth to minimize an angle of incidence between the incoming sunlight and the solar panel, thus maximizing the production of solar energy. For example, the panels are caused to move by the tracking systems so the solar panels face the sun as the sun moves from the East in the morning to the West in the evening.
A plurality of solar panels is typically coupled to a plurality of bars forming a plurality of solar panel rows. The bars typically run horizontally (in a North/South direction, for example). The solar panels rotate about the bars to track the sun from East to West. It is understood there are many varying types of mechanical tracking systems employed to rotate solar panels along one axis or more than one axis if desired. An example of a solar tracking system is described and shown in U.S. Pat. No. 8,459,249, the disclosure of which is hereby incorporated by reference in its entirety. A drive mechanism is disposed at one end of the rows.
Drive shafts connect adjacent ones of the solar panels in each of the rows via gearboxes so the solar panels move in unison to substantially track the sun simultaneously. It is desirable for the drive shafts to last a significant number of years such as up to 30 years, for example. Also, depending on the geographical location of the solar panels, the drive shafts need to withstand various types of environments. Typical drive shafts are formed with or a power take off (PTO) tube or a combination of a PTO tube and round tubes. Articulating joints or yoke assemblies are typically used to connect each end of the tube or tubes to the gearboxes. For example, a yoke assembly is used to connect the ends of each of the tubes to the gearboxes. The materials, compositions, and coatings used to form the tubes and the yoke assemblies are costly. For example, tubes can be made of hot dipped galvanized steel and the yoke assemblies may be formed from painted iron castings having properties which meet required torque requirements and endure various environmental conditions, which adds cost.
Additionally, the process of manufacturing the drive shaft tubes is inefficient and costly. The process typically requires components to be welded which increases manufacturing time and cost. Furthermore, due to variations in spacing between the panels in the rows, it is typically desired for the drive shaft to telescope up to 29 inches, for example. However, the galvanization process may cause imperfections within the mating surfaces of the PTO tubes which affects the telescoping. Therefore, it may be required to enlarge an end of the external PTO tube, which increases manufacturing cost and inefficiency.
Furthermore, undesired amounts of lash are present in the PTO tubes due to a variation of coating thicknesses on the tubes. The variation typically results from one end of the tube to the opposing end of the tube and from tube to tube due to large clearances between the parts of the drive line discussed hereinabove. The clearances further result in lash increasing as the coating wears. Since multiple drive shafts are working together (such as 27 for example) in a given row, controllability issues can result from the lash.
Accordingly, it would be desirable to provide a durable drive shaft for solar tracker systems that minimizes cost and complexity of manufacturing and assembly.